Help with checking gears

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I knows it's been posted before but I can't find it so I have to ask again. I wanted to check my ratio so I raised one rear tire and marked the axle and tire. The tire turned 1/2 when the axle turned 1. Then the tire turned slightly more than 1 when the axle turned 2 times. Then it just progressed from there, tire turning slightly more each time with the axle turning 1 time. Yesterday a friend told me something about a locking diff acting differently but I can't remember. Help please.

 

[big83chevy4x4]

jack one side of the truck. spin the tire 2 times and count how many times the driveshaft spins.

if you spin it 1/2 turn, yu have to multiply it x4. 1 turn x 2 and 2 turns x1. the more you spin the tire, the more accurate it is.

a locker will not allow you to spin the tire when one tire is on the ground.